With an increase in capacity of information processing in recent years, various information recording technologies have been developed. In particular, the surface recording density of an HDD using a magnetic recording technology is continuously increasing at an annual rate of approximately 50%. In recent years, an information recording capacity exceeding 500 gigabytes per disk has been demanded in a magnetic disk with a 2.5 inch diameter for use in an HDD or the like. To fulfill such a demand, an information recording density exceeding 700 GBit/square inch is desired to be achieved.
Further, in recent years, a perpendicular magnetic recording type in which a recording layer is magnetized in a perpendicular direction to a plane of a magnetic disk is adopted in order to further improve a recording density. In order to further enhance the recording density under these circumstances, both a linear recording density in a circumferential direction (BPI: Bit Per Inch) and a track recording density in a radial direction (TPI: Track Per Inch) must be improved while a predetermined S/N ratio is secured.
As a method for improving the track recording density, there is a method which narrows a recording head to reduce a track width. However, when the recording head is narrowed, such a problem occurs that, because a recording magnetic field density lowers, a sufficient S/N ratio cannot be secured. As a method for solving such a problem, therefore, a shingle write system in which information is written on tracks adjacent to each other in a partially overlapping manner has been proposed (for example, see Patent Document 1). Since the recording head can be formed largely by application of the shingle write system, such a merit is provided that the recording magnetic field density can be secured, the S/N ratio can be secured, and a track having a width narrower than a recording width of writing performed by an actual recording head can be achieved.